Bob Melvin of the Oakland Athletics and Washington’s Davey Johnson won big right away and were chosen as managers of the year Tuesday after guiding their teams to huge turnaround seasons.

Melvin beat out Baltimore’s Buck Showalter for the AL honor in a close vote by a Baseball Writers’ Association of America panel. In his first full season with Oakland, the rookie-laden A’s made a 20-game improvement, finished 94-68 and stunned just about everyone by winning the AL West with baseball’s lowest payroll.

Still, the unassuming skipper was surprised to win.

“Absolutely shocked. I mean, Buck had such a great year,” Melvin said on MLB Network.

Johnson was an easy choice for the NL prize after the Nationals _ who had never enjoyed a winning season _ posted the best record in the majors and made their first playoff appearance.

Johnson, who turns 70 in January, was honored for the second time. He was tabbed as the AL’s top manager in 1997, hours after he resigned from the Orioles in a feud with owner Peter Angelos.

This time, Johnson will get a while to enjoy the accolade.

The Nationals announced this month that he will guide them in 2013, when he will be the oldest manager in the majors. He’s set to leave the Washington dugout and become a team consultant in 2014.

“World Series or bust,” Johnson said on MLB Network. “It’s going to be my last year, anyway.”

Melvin also became a two-time winner, having been chosen in 2007 with Arizona. He and Johnson joined Jim Leyland, Bobby Cox, Tony La Russa and Lou Piniella as the only managers to win the award in both leagues.

La Russa was the only other Oakland manager to earn the honor, in 1988 and 1992.

Melvin received 16 first-place votes. Showalter got the other 12 firsts after leading the wild-card Orioles to their first winning season since 1997, and Chicago White Sox manager Robin Ventura finished third.

With five rookies in their starting rotation, the A’s were one of baseball’s biggest surprises this year _ especially after trades, injuries and the suspension of veteran pitcher Bartolo Colon wreaked havoc with the roster. Oakland never panicked under Melvin’s cool demeanor, rallied from 13 games back on June 30 and overtook Texas in the final week to win the division.

The Athletics went 72-38 after June 1, the best record in the majors. They became the first team in big league history to come back from a deficit of at least five games with fewer than 10 remaining to win a division or pennant. The A’s then lost in five games in the first round of the playoffs to AL champion Detroit.

“We just tried to keep it day to day,” Melvin said. “It’s a credit to the guys each and every day going out there and just worrying about that particular day.”

Johnson received 23 of the 32 first-place votes, Dusty Baker of NL Central winner Cincinnati got five firsts and was second. Bruce Bochy of the World Series champion San Francisco Giants got four firsts and was third.

Washington won its second major postseason award, both in the past two days. Bryce Harper was voted NL Rookie of the Year on Monday.

Washington went 98-64 this year, taking over the NL East lead in late May and staying in first place the rest of the way. Boosted by Harper, Cy Young Award candidate Gio Gonzalez and their fresh “Natitude,” they brought postseason baseball to Washington for the first time since 1933.

The playoffs didn’t go quite so well. Minus Stephen Strasburg _ team execs decided the ace had pitched enough in his first “full” season following elbow surgery _ Washington blew a 6-0 lead and lost the deciding Game 5 of the division series to St. Louis. Voting for the BBWAA awards was done before the playoffs.

Johnson oversaw a diverse roster, one made up of young and old, Washington veterans and newcomers. A four-time All-Star, three-time Gold Glover, two-time World Series champion and the last big leaguer to get a hit off Sandy Koufax, Johnson spoke with a soft, raspy tone but always held his team’s attention.

He would occasionally raise his voice _ he liked to holler “whack-o!” when the Nationals homered.

“Davey Johnson’s legacy was secure well before he became our manager in 2011, but his performance this season has to rate among his best work,” Nationals general manager Mike Rizzo said. “He showed this club how to win despite being engaged in a pennant race for the first time. And he accomplished this with so many young players.”

Johnson managed the New York Mets to the 1986 championship and later guided Cincinnati and the Orioles. He returned to managing in 1999 with the Los Angeles Dodgers for two years.

In June 2011, Johnson was working as a senior adviser with the Nationals when Jim Riggleman suddenly resigned midway through the season. Johnson took over and agreed to be part of a search committee to select a manager for 2012, allowing that he could be a candidate for the post, too.

The Nationals finished 80-81, barely missing out on their first winning season, and Johnson was brought back for another try.

Washington was without major league baseball for more than three decades. The Senators moved to Texas after the 1971 season, then the Montreal Expos moved to D.C. to start in 2005.

Under Johnson, the Nationals put aside their losing past and set up a winning future.

The same is true of the A’s. Fired by the Diamondbacks early in 2009, Melvin was hired as Oakland’s interim manager on June 9, 2011. Three months later, he signed a three-year contract that runs through the 2014 season.